The present invention relates to a liquid-cooled-type cooling device for cooling a heat-generating body composed of an electronic component such as a semiconductor device, and to a method of manufacturing the same.
The present applicant has proposed a liquid-cooled-type cooling device for cooling a power device (semiconductor device), such as IGBT (Insulated Gate Bipolar Transistor), which is used in a power conversion apparatus mounted on an electric vehicle, a hybrid vehicle, an electric railcar, or the like (see Japanese Patent Application Laid-Open (kokai) No. 2009-277768). The proposed liquid-cooled-type cooling device includes a casing having a cooling-liquid passage through which cooling liquid, including water (e.g., long life coolant) flows, and a radiating member fitted into an opening formed in the top wall of the casing. The radiating member is composed of a substrate whose first surface faces the cooling-liquid passage and whose second surface serves as a heat-generating body mount surface, and a plurality of pin-shaped fins integrally formed on the first surface of the substrate through forging such that the fins are staggered. A gap is provided between the distal ends of the pin-shaped fins and the bottom wall of the casing.
However, in the case of the liquid-cooled-type cooling device disclosed in the publication, since the pin-shaped fins of the radiating member are integrally formed on the substrate through forging, their dimensional accuracy in the height direction is insufficient. Therefore, the pin-shaped fins cannot be made uniform in height. Also, since the height of the pin-shaped fins is affected by the thickness of the substrate before formation of the pin-shaped fins, in order to secure a height of the pin-shaped fins sufficient for attaining a required heat radiation performance, the thickness of the substrate before formation of the pin-shaped fins must be increased. In such a case, after formation of the pin-shaped fins, the substrate has a relatively large thickness, which lowers the transfer of heat from a heat-generating body attached to the second surface to the pin-shaped fins, whereby the heat radiation performance becomes insufficient. The above-described problem of the liquid-cooled-type cooling device disclosed in the publication can be solved by machining the pin-shaped fins formed on the first surface of the substrate through forging, so as to make the pin-shaped fins uniform in height, and machining the substrate to thereby decrease the thickness of the substrate. However, in this case, the number of man-hours required for manufacturing the liquid-cooled-type cooling device increases. In addition, since the distal ends of the pin-shaped fins are not joined to the bottom wall, when the thickness of the substrate is decreased, the withstanding pressure of the liquid-cooled-type cooling device may become insufficient.